Adjustable resistance devices



Dec. 29, 1959 R. L. HARTUNG 2,919,400

ADJUSTABLE RESISTANCE DEVICES Filed Feb. 20, 1958 s Sheets-Sheet 1 WRITER ELECTRIC TYPE- H 8@ E, 9 w m L t 7+ \w w i INVENTOR K) ROBERT L.HARTUNG ATroRNEY5 Dec. 29, 1959 R. L. HARTUNG 2,919,400

ADJUSTABLE RESISTANCE DEVICES Filed Feb. 20, 1958 3 Sheets-Sheet 2 E34 8 68 gi Q 2;. INVENTOR ROBERT L.HARTUNG ATTORNEYS Dec. 29, 1959 R. L. HARTUNG 2,919,400

' ADJUSTABLE RESISTANCE DEVICES Filed Feb. 20, 1958 v 3 Sheets-Sheet 3 UNITS TENS FIG. 7.

HUNDREDS INVENTOR U ROBERT uumwus S .0 t. g MW 9 9) o o:

*- Em ATTORNEYS related with the indicia carrying member.

United States Patent'O 2,919,400 ADJUSTABLE RESISTANCE DEVICES Robert L. Hartung, Fort Worth, T ex., assignor to B 8: H 1 Instrument Company, Inc., Fort Worth, Tex., a corporation of Texas Application February 20, 1958, Serial No. 716,350 7 Claims. (Cl. 32463) This invention relates to adjustable resistance devices of the type described and claimed in the copending application of R. A. Williams, Serial No. 572,758, filed March 20, 1956, now Patent No. 2,860,215, assigned to the assignee of the present invention. The present application is a continuation-in-part of my application of this title filed November 7, 1957, Serial No. 695,033, now

abandoned.

The aforesaid Williams application describes and claims an apparatus wherein indicia items are located along an indicia carrying member, for example, a broad tape, at positions therealong determined by the actual measured electrical resistance of a resistance element properly cor- The resistance element may be a distinct item coupled for movement with the indicia carrying member, or the resistance element may be an integral part of the member, as Where indicia are placed on a tape which is itself of electrically conductive material having predetermined resistance characteristics. The indicia may be in the form of a succession of printed numbers, or any other sensible manifestation such as punched apertures, conductive areas, and so forth, which may be sensed by the eye or by sensing apparatus to convey information.

The present invention concerns an arrangement within the broad invention of the aforesaid application, for a particular form of said indicia and use thereof. Briefly stated, the indicia is in the form of a series of engageable configurations such as apertures along the indicia member which cooperate with complementary engageable configurations on a cooperating member, such as teeth on a sprocket wheel, the latter being used to drive a record keeping and/or displaying apparatus, such as a counter. The particular point of the present invention is that an aspect such as the spacing between the engageable configurations along the indicia carrying member are varied in accordance with actual electrically measured values of resistance and as a consequence the output device keeps step with variations in resistance from point to point along the resistance element.

Accordingly, it is a primary object of this invention to provide novel forms of indicia and means cooperating therewith in apparatus of the aforesaid type.

Another object of this invention is to have the aforesaid cooperating means provide a digital output.

Further objects and the entire scope of the invention will become more fully apparent from the following detailed description of an exemplary embodiment of the invention, which can be best understood with reference to the accompanying drawings, wherein:

Figure 1 shows an assembly of components demonstrating the principles of the invention.

Figure 2 shows a plan view of a segment of the indicia carrying member of the invention and indicia thereon.

Figure 3 shows a side elevational view partly in section of a segment of the indicia carrying member and a segment of a sprocket Wheel engaging apertures in the member.

Figure 4 shows a cross-sectional view substantially along the line 4-4 of Figure 3.

Figure 5 shows a top plan view partially in section along the line 5-5 of Figure 3.

Figure 6 shows a digital output device in accordance with the invention, and

Figure 7 is a chart of digital values produced by the device of Figure 6.

Referring to Figure 1, reference character 10 designates an indicia carrying member in the form of a broad tape reelable between spools 12 and 14. An electrical contact member 16 is mounted by suitable means (not shown) for engaging a resistance element 18 affixed to one edge of the indicia carrying member 10. A small section of element 18 is shown broken away adjacent reference character 18 to provide a better understanding. However, it will be understood that the member 10 may itself be of electrically conductive material having resistive characteristics and the contact 16 will simply contact the material of member 10 per se. Various forms of indicia carrying members of insulating material with separate resistance elements afiixed thereto or driven thereby are fully described in the aforesaid copending application and no detailed discussion is thought to be necessary herein. The aforesaid application also fully explains how indicia may be placed directly on a resistance element, in which case it can be said that the resistance element is an integral aspect of the indicia carrying member.

In Figure 1 the indicia are in the form of a series of apertures 20 arrayed along the lengthwise direction of the indicia carrying member 10. A sprocket Wheel 22 having a plurality of regularly spaced teeth 24 is rotatably mounted by a suitable means (not shown) so that the sprocket teeth engage the indicia apertures in rack-and-gear fashion. The sprocket wheel 22 is aflixed to a shaft 26 coupled to drive an output device, illustrated in the form of a Veeder Root counter 28. The output device may be selected from a variety of available apparatus which also provides an electrical output, which can be on line 30 for controlling a printing device such as an electric typewriter 32 which can be arranged to print successive numbers or the like on a strip of paper 34 issuing therefrom. The output device may provide digital manifestation as discussed hereinbelow.

In accordance with the present invention, when the indicia carrying member 10 occupies a given position with respect to contact 16 a particular indicia aperture such as that one designated 20 in Figure 1 will be physically located on the indicia carrying member with the intention that this physical location convey information as to the actual measured value of resistance where contact 16 makes its engagement. The particular indicia 20 might be located exactly opposite the point of engagement of the contact 16 with the member 10, but it should be understood that there can be any desired stag ger distance S and the same principles will apply.

Additionally referring to Figure 2, it is the contemplation of the illustrated embodiment that the engageable indicia apertures 20 will be per se of the same dimensions. The lengthwise dimension is the important one in the illustrative embodiment being described and from Figure 2 it will be understood that this dimension of each aperture 20 is equal, and denoted by the letter L. However, and this illustrates a particular point of the present invention, the lengthwise spacing between corresponding points on successive apertures 20 isnot constant, but may vary according to variations in pregressive electrically measured values of resistance where the contact 16 engages the resistance element. Variable spacings are suggested by the letters a and a showing the spacings of the apertures 20 in Figures 1 and 2. In the illustrative embodiment it is contemplated that all of the teeth 24 of sprocket wheel 22 will be spaced equal distances, the angle A in Figure 1. Comparing with Figure 2, the equivalent A of the tooth spacing is indicated, and it will be seen that the actual spacing a is slightly less than A. Additionally, in Figure 2 the distance a is slightly greater than A. The situation illustrated in Figure 2 represents a case where a given change in electrically measured resistance has occurred which is represented by the spacing a but the same change in electrical resistance from the middle to the right-hand aperture 20 has required a greater movement of the member 10.

Referring to Figure 3, it is preferred that the engageable configuration on the indicia carrying member 10, the apertures 20 of length L in the illustrative embodiment, be so designed in relation to the complementary engaging member, specifically in Figure 3, a tooth 24, that there will be certainty that the indicia carrying member self-center itself. In the case of the aperture 29 in the indicia carrying member and the sprocket tooth 24, it is preferred that the tooth range between a dimension T at its base to an apex dimension T with the distance L being findable between the base and apex. As illustrated in Figure 3, this will insure the centering of the aperture 20 on the tooth somewhat above the base of the tooth and backlash or lost motion is prevented.

Still referring to Figure 3, the design of the cooperating members and 22 should be such that for at least the position shown in this figure, there is positive centered engagement at one tooth and at the same time the other teeth are free of direct interfering engagement with the member 10.

While in the illustrative embodiment as thus far described each aperture is of the same length L, it will be apparent and it is within the scope of the present invention that the apertures, in fact, can be of different lengths, or other designs of engageable configurations can be relied upon, so as to provide a result which is the functional equivalent of variously distributing equally sized apertures for carrying out the purposes of the invention. For example, ridges on the member could cooperate with sprocket teeth. No limitation is intended.

As can be understood in detail from the aforementioned copending Williams application, the operation of the device will normally involve an electrical circuit of some type between the contact 16 and one or both ends of the resistance element 18. For purposes of brief demonstration in the present application, there can be an electrical circuit comprising electrical conductors to connect in series contact 16, a current meter 42, some type of utilization circuit 44, a source of potential such as battery 46 and a suitable slip ring 47 if desired to the end of resistance element 18 at the hub of reel 14. A typical utilization circuit would be a potentiometer, wherein the resistance element 18 forms one arm of a balancing bridge.

In operation, the indicia carrying member 10 with resistance element 18 will be moved back and forth from reel to reel with respect to contact 16 by some prime mover, which can be a knob 50 for manual operation or could be a servo motor or an interconnection with some moving part of associated apparatus. It is possible that the drive could be imparted to the sprocket wheel itself, and the latter drive the tape.

The aperture 20 in the member It will have been created by some technique such as providing a known and constant potential source at 46 and a known resistance at 44 so that readings of the meter 42 can be interpreted in terms of ohms of resistance of the element 18 (or the resistance of the indicia carrying member 10 if it has resistive characteristics). Assuming the output device 28 is arranged to change a digital reading in response to annular movement A (the digital values may be in ohm O in degrees centigrade or any other unit, depending upon the nature of the intended utilization circuit 44), the first aperture will be punched with the meter 42 reading a given amount, the member 10 and element 18 then moved with respect to contact 16 a distance so as to cause the meter 42 to have advanced one unit, whereupon the next aperture 20 will be punched. The further moveent necessary to cause the meter to add a unit will be accomplished and then the next aperture will be punched, and so forth. If the resistance element 18 was absolutely uniform along its length (which is not true in practice) all of the apertures 20 would be equally spaced. However, due to unavoidable variations in the resistance characteristics of the element 18 along its length, movement sufficient to add each unit of electrical measurement will be represented by differing distances of movement, resulting in the apertures being spaced apart varying distances as was explained with reference to Figure 2.

As an alternative method of placing the indicia, this can be accomplished by a voltage divider method. That is, a circuit (not shown) can be provided using voltage divider principles so that the voltage at contact 16 is zero when compared to a known voltage at which the apparatus is calibrated. This procedure renders the contact resistance of contact 16 unimportant. The tape may be calibrated as a direct voltage or as a ratio voltage.

Having the apertures thusly located, it will now be understood that as the indicia carrying member and resistance element move with respect to the contact 16, the reading of the output device will at any instant show the true electrically measured value of the resistance because the indicia carrying member 10 will be at a position as shown in Figure 3 with respect to the means 22 engageable therewith. Stated otherwise, as the movement progresses, there will be differential adjustments to the general rack-gear movement of the member 10 with respect to the member 22. The situation is distinguished from the ordinary rack-gear movement wherein the engageable means on the rack are equally spaced to cooperate with equally spaced teeth of the gear.

It should be understood that the indicia such as punched apertures may be spaced along the indicia member upon one of several basis. For example, if the indicia are to be placed as strictly a linear function, then the positions of same are varied strictly in accordance with the non-linearity of the resistance of the resistance element. However, if a curve to be followed by equipment incorporating the device of this invention is a nonlinear curve such as a curve of chromel-alumel of a thermocouple circuit, then the indicia may be spaced due both to the non-linearity of the resistance of the resistance element and also due to the non-linearity of the chromel-alumel curve.

It may be desirable to have a positive self-centering action of the tape 10 with respect to the sprocket wheel 22 in the illustrative embodiment. Depending upon the forces existing between the sprocket teeth and the edges of the apertures 20, there might be a tendency for the tape 10 to slide upwardly along one face or the other of a tooth 24 (refer to Figure 3) which would result in loss of positive centering. As illustrated in Figures 3, 4 and 5 such action can be precluded as by the use of. a shoe 60 and associated parts which will now be described. It may be mentioned at this point that shoe 60 and associated parts are not shown in Figure 1 in order to avoid a confusion in the vicinity of the engagement of the sprocket wheel 22 with the tape 10 in that figure.

Shoe 60 may be of polished material so as to not injure the tape 10, and the shoe may have upwardly curved ends 6th: and 60b to facilitate the sliding of the tape through. The shoe 60 will be provided with an elongated slot 62 for accommodating the teeth 24 intermediate said ends tida and 60b. Movement of the shoe along with the tape can be precluded by use of transverse retaining members 64 at each end of the shoe,

supported by suitable structure, and 'so arranged that shoe 60 will be slidable up and down therebetween. Shoe 60 can be urged downwardly onto the top of tape by a bridge piece 66 which has downwardly extending legs 68 at each end which are pointed at their lowermost extremities and set in suitable detents (not shown) in the top surface of the shoe 60. A spring 70 acting at one end against a suitable fixed support 72 may be employed to urge a slidable pin 74 downwardly toward bridge 66 so that head 76 of the pin is urged into a de tent in the top of bridge 66. The result will be the continuous urging of the tape 10 downwardly on the sprocket teeth and climbing of the edges of the apertures 20 up one side or the other of the teeth will be precluded. It will be understood that many other arrangements can be provided for insuring correct engagement of the tape with the cooperating engageable means and no limitation to the components just described is required.

An output arrangement according to a feature of the present invention may be constructed to produce digital output values, for extremely high accuracy and general convenience. Referring to Figure 6, the output shaft 26 (Fig. l) of the indicia sensing device may drive a units segmental switching device arranged so that an electrical wiper contact 80 revolving with shaft 26 sequentially wipes over conductive segments designated 82. In the illustrative example given in Figure 6, in the units stage there are eight segments 82 with those numbered 1, 3, 5 and 7 collectively connected to an output conductor 84. The segments 82 are stationary and therefore during one revolution of shaft 26 the wiper 80 will sequentially pass over all eight of the segments 82. Of course, contact 80 could be stationary and the segments movable. Additionally, there may be provided a tens wiper assembly and at hundreds wiper assembly, as well as ones for thousands, etc. (not shown). Between each stage there is a suitable rotary reduction mechanism 86 for causing only a one segment increment movement of the following stage when the previous stage rotates a full revolution. That is, the tens wiper will move only from one segment 82 to the next upon a full revolution of the units Wiper. The segments 82 of the tens unit may be collected on output line 88 so that only segments 2, 3, 6 and 7 are connected thereto. In the hundreds stage only segments 4, 5, 6 and 7 are connected to output line 90. (It will be apparent that the unconnected segments 82 can be dispensed with: these have been shown in Figure 6 only to expedite an understanding of the arrangement.) Shaft 26 and the wipers 80 of each stage may be electrically connected together by a suitable slip-ring connection 92 which may be connected to the grounded side of a potential source 94, the other side of which may be connected in common to one input of suitable loads or indicating devices 96 for each stage. To insure reading or operation of the load means 96 only when the wipers 80 are adequately centered on segments 82, the shaft 26 may carry a makeand brake contact wheel 98 having a number of contact points 100 bearing some relationship to the number of sprocket teeth 24 or the like. A contact 102 may make circuit to ground with the contact points 100 and thusly energize relay coil 104 to close a circuit between contacts 106 and 108 in the circuit between the potential source 94 and the loads 96. The remaining input to each load 96 is connected to one of the stage output lines 84, 88, 90, etc.

It will now be apparent that the operation of the arrangement in Figure 6 will provide at loads 96 a typical binary digital output. Figure 7 is a chart of the possible numbers as a function of the position of the wipers. It will, of course, be appreciated that any of the typical binary systems can be utilized and no limitation to the particular number of stages, number of segments 82, etc. is necessary or intended.

In many cases it will not be necessary to utilize the apparatus described above to positively center the apertures on the sprocket teeth. If the apertures are, for instance, 0.070 inch wide and a sprocket tooth is only 0.040 inch, there is an 0.030 inch difference or error. If the aperture spacings are approximately 0.150 inch and there are 1,000 apertures along the indicia member, then the 0.030 inch error may well be insignificant in the total length of the indicia member, being in the order of 0.02%. The main point is to not permit small errors to accumulate, which is accomplished by causing the spacings to have the differential variation in strict relationship to actually electrically measured values of resistance of the resistance element, or this superimposed upon variations in a functional curve to be followed.

As compared to the cases where the indicia may be visible numbers, or groups of apertures sensed by electrical or mechanical feelers, 'etc., the present invention is particularly useful where due to limitations upon the width of the member 10 or otherwise it may be desirable to have the more complex sensing equipment at a remote point, or where the components shown in Figure 1 must be located at some position remote from a human operator. By any conventional telemetering circuits a number visible to the human eye can be established at any remote point. And as hereinabove indicated an electrical output may drive a device such as an electric typewriter which keeps printing a running account of the readings from the adjustable resistance device. For example, the output tape 34 of device 32 could be provided with a means for printing an additional column 52 of figures for showing time of day or date, the position of a part of a machine in which the adjustable resistance device is inoperative, or any other data to be compared with the reading which is in terms of the electrical resistance of the element 18.

In any of the above described embodiments, it should be understood that there may be reduction or amplification gearing between the sprocket wheel or other device which follows the indicia, and the output device, such as the counter. For example, the output device can be geared as a ratio to the indicia such as apertures in ratios of A, 5 times, 10 times, etc.

As heretofore indicated the detailed description of the illustrative embodiment of the invention is given only for purposes of explaining the basic principles of the present invention and the true scope of the invention is to be determined from the appended claims.

What is claimed is:

1. In a resistance device of the type having an indicia carrying member whereon indicia are positioned in terms of actual electrically measured resistance values of the member itself or of a resistance element which is coupled for movement with said indicia carrying member; indicia on the member in the form of successive engageable configurations along said member, an indicia engaging member having a configuration thereon for engaging with said configurations on said member, an output device coupled with said indicia engaging member, means for mounting the indicia engaging member in position such that the configurations of said member engage said configuration on the indicia carrying member as the member moves in a predetermined path with respect to the indlcia engaging member, a positional aspect of said engageable configurations on said indicia carrying member being varied in accordance with variations in said electrically measured values of resistance, the arrangement being such that the output device coupled to the indicia engaging member keeps step with actual measured resistance values of the resistance element.

2. In a resistance device of the type having an indicia carrying member whereon indicia are positioned in terms of actual electrically measured resistance values of the member itself or of a resistance element which is cou- 7 pled for movement with said indicia carrying member; indicia in the form of successive apertures along said member, a sprocket wheel having a plurality of teeth thereon for engaging said apertures, an output device coupled with said sprocket wheel, means for rotatably mounting the sprocket wheel in position such that successive teeth thereof engage apertures as the member moves in a predetermined path, a characteristic of said apertures on said member being varied in accordance with variations in electrically measured values of said resistance, the arrangement being such that the output device coupled to the sprocket wheel keeps step with actual measured resistance values of said resistance.

3. A device as in claim 2 wherein the output device is an apparatus arranged to display data which is variable in response to variations in the angular input from the sprocket wheel.

4. A device as in claim 1 wherein the output device includes means for printing successive data characters as the indicia engaging member changes its angular position.

-5. A device as in claim 2 wherein the apertures are each of equal size but spaced apart differing distances in accordance with said measured values of resistance.

6. A device as in claim 1 wherein the output device includes means for concurrently providing a plurality of electrical signals representing a digital output.

7. A device as in claim 6 wherein the output device comprises a plurality of stages for at least units and tens values, and includes rotary reduction apparatus between said stages.

References Cited in the file of this patent UNITED STATES PATENTS 2,275,977 Means et a1 Mar. 10, 1942 2,629,843 Berry Feb. 24, 1953 FOREIGN PATENTS 930,536 France Ian. 28, 1948 

